There has recently been developed a type of electronic musical instrument which is an arrangement in which a plurality of order pulse generators and a plurality of musical-tone waveform forming circuits are connected in order to the output side of a tone-source-signal pulse generator. The order pulse generators each comprises an address counter, which is composed of a plurality of one-half frequency-dividers connected in series so that a plurality of frequency-divided pulses can be generated from the output terminals of these frequency-dividers. Also included is a matrix circuit, which operates in such a manner that the frequency-divided pulses are decoded thereby and a plurality of order pulses can be taken out in order from the output terminals thereof. The musical-tone waveform foming circuits each comprises a musical-tone-waveform memory circuit which has a sampling number (that is, the set values previously memorized are read out by the order pulses and are converted into digital signals constituting output signals) corresponding to the number of previously mentioned order pulses from 1 to n, and a digital-to-analog converter which operates in such a manner that the digital signals obtained in order therefrom are converted into analog signals to form a musical-tone signal.
If, for example, the pulse oscillation frequency of the tone-source-signal pulse generator is f, the output signal thereof (that is, a series of pulses) is decoded by each order pulse generator and converted into order pulses of from 1 to n, and one musical-tone waveform is formed from the order pulses of from 1 to n by each tone waveform forming circuit and thus a musical-tone signal of frequency f/n can be obtained. The above is disclosed, for example, in U.S. Pat. No. 3,515,792.
With this arrangement, for obtaining musical-tone signals extending over a wide octave range, the oscillation frequency f of the tone-source-signal pulse generator 1a must be set very high such as, for example, at 2.00024 MHz and the number of order pulses n at each of the order pulse generators must be set, for example, at 239, 253, . . . 451, 478 . . . etc. The fact that the number n must be varied as above results in disadvantages including that the respective sampling numbers of the musical-tone waveform memory circuits of the musical-tone waveform forming circuits must be differentiated from one another and that these must be numerous. Thus, the manufacture and adjustment thereof is relatively troublesome.